1. Field of the Invention
The present invention relates to a self-developing photo film unit. More particularly, the present invention relates to a self-developing photo film unit in which a trap member is reliably capable of capturing a surplus part of developing solution without enlarging a size of a portion wrapping the trap member.
2. Description Related to the Prior Art
There is a mono-sheet type of self-developing photo film unit for use with an instant camera. The photo film unit is constituted by a combination of a photosensitive sheet, a mask sheet, a cover sheet and the like. After the photosensitive sheet is exposed, a developing solution pod is squeezed and torn by spreader rollers of the instant camera. Developing solution, contained in the developing solution pod, is spread between the photosensitive sheet and the cover sheet. There occurs a surplus part of the developing solution in a small amount. The surplus developing solution remains in a bendback edge portion of the mask sheet. A trap member is enveloped in the bendback edge portion, and traps or captures the surplus developing solution.
There are various examples of photo film units different in size, including Photorama Film (trade name) manufactured by Fuji Photo Film Co., Ltd. with a size of 97.times.102 mm, Joycam Film (trade name) manufactured by Polaroid Corporation with a size of 64.times.111 mm, and Xiao Film (trade name) manufactured by Polaroid Corporation with a size of 30.times.160 mm.
Recently there has been an idea of reducing the overall size of the photo film unit in consideration of reduction of the size of an instant camera. At the same time, a frame size of the photo film unit should be kept sufficiently large. Thus it is desired to reduce a width of the bendback edge portion containing the trap member. In the course of taking an instant photograph, the surplus developing solution is absorbed immediately after the developing solution is spread. The developing solution exists in the vicinity of the trap member in a temporary manner with high fluidity. Swelling of the trap member requires comparatively much time. If a user manually grasps the trap member immediately after the development, the surplus developing solution is very likely to flow out of gas vents or air holes.
Although the above-mentioned various sizes exist for the photo film units, there is no known photo film unit easy to be handled for preservation after taking an exposure. To facilitate the handling, the size of the photo film unit should be reduced further. However excessive smallness of a photo film unit causes reduction of the frame size. If a number of people are photographed in a single frame, it is likely that faces of those people cannot be recognized clearly by viewers.